Prediction of fatigue limit improvement in needle peened welded joints containing crack-like defects
Prediction of fatigue limit improvement in needle peened welded joints containing crack-like defects
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含有裂纹缺陷的针喷焊接接头疲劳极限改善的预测
DOI：
10.1108/ijsi-03-2017-0019
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发表时间：
2018
影响因子：
2.7
通讯作者：
Koji Takahashi
中科院分区：
文献类型：
--
作者：
Ryutaro Fueki;Koji Takahashi
本文的目的是估算奥氏体不锈钢焊接接头在喷丸后可接受的缺陷尺寸，并预测使用喷丸后疲劳极限的改善。观察了焊趾周围的显微组织，以阐明NP处理后硬度变化的原因。采用有限元分析方法，分析了NP术后应力集中的变化。采用断裂力学方法对NP术后的Amax进行评价。通过测定不同应力水平下的应力幅值，预测了NP前后的疲劳极限，发现NP前焊趾表面产生的拉伸残余应力转变为NP后的压缩残余应力。NP后表层附近的残余应力超过了NP之前的屈服应力，这是由于加工硬化导致的屈服应力的增加以及形变诱发马氏体组织的产生。由于NP对形状的改善，降低了应力集中。实际应用表明，该方法可用于提高大型钢结构、运输设备和工业机械等焊接接头的可靠性。从工程角度看，估算含裂纹缺陷焊接接头的MAX和疲劳极限是十分必要的。然而，目前尚不清楚是否有可能预测Amax，以及Np对不锈钢焊接接头疲劳极限的影响。
PurposeThe purpose of this paper is to estimate the acceptable defect size amax after needle peening (NP) and predict the fatigue limit improvement through the use of NP for an austenitic stainless steel welded joint containing an artificial semi-circular slit on a weld toe.Design/methodology/approachResidual stress and hardness distribution were measured. Microstructures around the weld toe were observed to clarify the cause for the change in hardness after NP. Finite element method analysis was used to analyze the change in the stress concentration following NP. Fracture mechanics was used to evaluate amax after NP. The fatigue limits before and after NP were predicted by determining amax for several levels of stress amplitude.FindingsThe tensile residual stress induced at the surface of the weld toe prior to NP changed to a compressive residual stress after NP. The residual stress near the surface layer after NP exceeded the yield stress prior to NP due to the increase in yield stress as a result of work hardening as well as the generation of a deformation-induced martensitic structure. The stress concentration was reduced due to the shape improvement caused by NP. The estimation value of amax after NP and the prediction results of fatigue limits were in good agreement with the fatigue test results.Practical implicationsThe proposed method is useful in improving the reliability of welded joints used in large steel structures, transportation equipments and industrial machines.Originality/valueFrom an engineering perspective, it is essential to estimate amax and the fatigue limit of welded joints with crack-like defects. However, it is unclear as to whether it is possible to predict amax and the effects of NP on the fatigue limit for stainless steel welded joints.
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